1. Field of the Invention
The invention relates to a sucking jet pump having a tubular casing, said pump being described in claim 1.
Sucking jet pumps of the abovementioned type are used in brake booster systems having a vacuum brake booster. In this case, the sucking jet pump is used to increase the vacuum in the brake booster connected to a vacuum generator.
2. Background Invention
In known systems of this type, the sucking jet pump is inserted into a suction line leading from the brake booster to the vacuum generator, in order, as required, to reinforce the suction line of the vacuum generator. For this purpose, the vacuum generator is connected, on the outlet side, to an air supply nipple arranged on the casing of the sucking jet pump, laterally relative to the throughflow direction. By pressurized outlet air from the pressure generator being supplied to the sucking jet pump, the flow is accelerated in the latter and an additional vacuum is generated. In order to prevent pressure equalization between the vacuum generator and the volume of the brake booster, a nonreturn valve is provided between the brake booster and the sucking jet pump in the casing of the latter.
A sucking jet pump designed in this way is known from DE 43 10 761 C2. The action of this known sucking jet pump cannot be criticized, but the casing is difficult to produce, since it forms both flow channels as a result of intermediate walls integrally formed in one piece and the conical path or shape of the first flow channel presents further difficulty in injection molding terms when the individual walls are to have approximately the same thickness. Moreover, a disadvantage of this embodiment of the sucking jet pump is that the entire sucking jet pump has to be modified when its suction capacity is to be varied.
Particularly in order to avoid the last-mentioned disadvantage, it is proposed, in DE 19 512 700 A1, to introduce into the first flow channel a separate nozzle insert which has the cross-sectional narrowing. Nevertheless, in this embodiment, it is still necessary to divide the interior of the casing into two flow channels by arranging inner walls. The separately formed nozzle insert is inserted firmly into one of these two flow channels, sealing relative to the outside. This embodiment of the sucking jet nozzle does not lead to simplified production of the casing and, furthermore, also has the disadvantage that an additional component has to be produced, and introduced into the casing, for the narrowing of the cross section of the first flow channel.